1. Field
This disclosure relates generally to micro-electro-mechanical systems (MEMS) devices, and more specifically, to a MEMS inertial sensor with frequency control and method.
2. Related Art
In the development of MEMS inertial sensors, a need has arisen to dynamically measure the frequency offset between the drive and sense resonators in a MEMS gyroscope. It would be desirable to provide such dynamic measurement that is characterized by one or more of the following: 1) does not interfere with normal MEMS gyro operations; 2) does not corrupt the MEMS gyro data; 3) tunable and adaptable without hardware design modifications; 4) useful for manufacturing calibration; 5) can be calibrated to absolute frequency offsets; and 6) can recover the injected frequency, reject data and spurious signals, and achieve the same at very low cost.
Further in connection with MEMS gyroscopes, it would be desirable to provide a tunable, low frequency oscillator to allow certain calibration and operational measures. However, the low frequency oscillator should not be derived from the drive resonator. In addition, the silicon die area, power, frequency and amplitude stability of an ASIC based oscillator operating at several hundred Hz is prohibitively expensive. Furthermore, with such a low frequency oscillator, there exists the need for a very narrow bandwidth, low frequency tunable filter. Such a very narrow bandwidth, low frequency filter can be prohibitively expensive to include on an ASIC at the sub-kilo Hertz frequencies.
Accordingly, there is a need for an improved method and apparatus for overcoming the problems in the art as discussed above.